“Nobody thinks any of these weapons are going to be used deliberately, but miscalculation is a significant chance,” added Browne, who chairs the Euro-Atlantic Security Leadership Group.
It’s a concern shared by current and former nuclear security officials who usually don’t agree on much — from disarmament advocates to nuclear hawks.
“I think the Ukraine conflict is demonstrating that the nuclear escalation scenario we’re worried about is not out of sight,” said Patty-Jane Geller, an expert on nuclear strategy at the hawkish Heritage Foundation.
Last week, the Bulletin of the Atomic Scientists cited the Ukraine conflict as contributing to its decision to keep the “Doomsday Clock” at 100 seconds to midnight, an indication of how close it assesses that the human race is to potential self-annihilation.
“Ukraine remains a potential flashpoint, and Russian troop deployments to the Ukrainian border heighten day-to-day tension,” it noted in citing the threat of a nuclear conflict.
A primary concern, according to Geller and others, is Russia’s arsenal of thousands of battlefield nuclear weapons, which are central to its military strategy.
“The Russians have something like 4,000 [tactical nuclear weapons] and they have an ‘escalate to win’ nuclear doctrine, which says ‘we use nuclear weapons first if the conventional conflict starts to spin out of our favor,’” said a former senior GOP government official who still works on nuclear security issues.
One Russian diplomat last month went so far as to publicly threaten the deployment of tactical nuclear weapons in the crisis.
The weapons have a lower “yield” than traditional atomic bombs and are designed to be used against conventional forces in battle. But they still have enormous explosive power and are considered particularly destabilizing to deterrent strategy.
The United States has reportedly been flying dedicated spy missions over in recent weeks to determine if Russia has deployed any of its tactical nuclear weapons along the border with Ukraine.
There’s also concern among Russian nuclear experts about the potential that the Ukraine crisis could escalate, according to former U.S. Ambassador Richard Burt, who negotiated arms control treaties with the Soviet Union.
He told POLITICO he was on a conference call Wednesday with European and Russian security officials and experts who discussed just such a scenario.
“People are worried about the possibility … through some process of escalation this somehow gets out of control — misreading, misunderstanding signals, or technical mistakes — [and] that nuclear weapons in one form or another could become a factor in this crisis,” he said.
The situation is exacerbated by the growing number of U.S., NATO, and Russian military forces in close proximity, Burt said.
“One thing I think is useful to remember is people are not just putting their forces on alert in and around Ukraine, but you’ve got nuclear-capable naval forces in the Black Sea and in the Mediterranean,” he said. “In the Baltic Sea there also has been an intensification of activity as well. You have a lot more aircraft flying overflights.”
Russia has also been nuclear saber-rattling in recent days, threatening that if NATO doesn’t meet its demands for halting the alliance’s expansion east it could deploy its tactical nuclear weapons closer to American borders.
“What we should be worried about is their doctrine and their 4,000 non-strategic nuclear weapons,” the former official added.
Another concern is that many of its military aircraft and missiles are also designed to carry both non-nuclear and nuclear weapons, a circumstance that could sow even more confusion during hostilities.
“It is very difficult for the West to know, ‘that conventional or nuclear,’ until it’s used,” the former nuclear official said, citing in particular air defense systems.
Nikolai Sokov, a former Russian Foreign Ministry official, said he considers the risk of a conflict over Ukraine spilling over into the nuclear arena as “extremely remote.”
But even he says it’s conceivable that one or both sides could dangerously miscalculate. For example, an accidental clash between Russian and NATO aircraft or warships, he said, “may trigger direct confrontation and then it could roll.”
For leading advocates of reducing nuclear arms, the Ukraine crisis highlights the hugely destabilizing role they play.
“What are nuclear weapons doing for us?” asked Tom Collina, director of policy at the Ploughshares Fund. “We only kind of think about them when we get into these crises, where really all they become is a liability.
“It’s hard to argue that nuclear weapons are adding to anybody’s security in this situation, but they seem to be the thing you can stumble into by mistake,” he added.
Also looming over the crisis is Russia’s history of using cyber-attacks as a key element of its military strategy, which could potentially disrupt or confuse nuclear command and control systems.
Chris Painter, a former top government cyber official, warned this week of the risk of a nuclear escalation caused by a cyber attack impacting nuclear forces.
“We do know that Russia and other services are intent on intruding into U.S. systems,” he told an event hosted by the nonprofit Nuclear Threat Initiative. “Obviously, nuclear command and control would be a target they’d want to go after and get a foothold in. This is a really dangerous thing … if those systems are seen to be unreliable … that does have a real effect on deterrence. It’s hugely escalatory.”
Others have taken issue with American rhetoric that they see as sowing unnecessary confusion about what military options might be under consideration to prevent a Russian invasion of Ukraine.
Repeated assertions that “all options are on the table” to punish Moscow should it reinvade Ukraine are seen as particularly troubling.
“In the nuclear age, ‘all options on the table’ in a conflict involving nuclear powers could be understood to mean the potential use of nuclear weapons, even if that wasn’t the intention in this instance,” two leading arms control advocates wrote last week.
“U.S. and Russian leaders must consider the use of such weapons off the table — there are no winners in a nuclear war,” they added.